Solvent for degreasing iron and aluminum



Patented Feb. 3, 1948 Walter Klabunde, Niagara Falls, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmmgton, DeL, a corporation of Delaware No Drawing. Application August 24, 1945, Serial No. 612,548

2 Claims. (Cl. 252-172) This invention relates to the prevention of trichlorethylene decompositionas catalyzed by the presence of aluminum or iron, particularly as is encountered in the metal vapor degreasing. I It is known that trichlorethylene when'exposed to air, light, and heat decomposes by oxidation with the formation of dichloracetyl chloride, hydrochloric acid, and phosgene. Several types of stabilizers are commonly used to inhibit the decomposition of trichlorethylene by oxidation. However, in metal degreasing, where the solvent often is subjected to higher temperatures, trichlorethylene, can undergo a condensation-type decomposition to form hydrochloric acid together with a resinous material. aluminum or iron the hydrochloric acid formed by either type decomposition reacts with these metals to form the chlorid salts which act as catalysts for the condensation reaction. Thus, when th condensation reaction takes place in a metal degreaser where the chips of th se metals are often heaped in the boiling solvent, it often becomes autocatalytic, i. e., wher aluminum is present, the hydrochloric acid forms aluminum chloride which decomposes more trichlorethylene to form more catalyst. Whenthis occurs, the solvent decomposes very vigorously with the evolution of large quantities of hydrochloric acid and the formation of a tarry or gummy mass in the solvent.

Efforts have been made in the past to combat this type of decomposition of the trichlorethylene by the addition of water to the solvent. This practice has only been partially successful primarily due to the low solubility of water in trichlorethylene. Certain alcohols have also been used in this connection. However, the addition of alcohols increases the solubility of hydrochloric acid in trichlorethylene and thus is undesirable in metal degreasing because of corrosion difficulties encountered.

vide a stabilizer for trichlorethylene which will The object of the present invention is to prowamhmam inhibit the condensation type of decomposition which is catalyzed by the presence of aluminum or iron. Another object of this invention is to provide a condensation inhibitor for trichlorethylene which is neutral to the solvent and can be readily recovered with the solvent and need I. only be present in relatively small concentration.

A further object is to degrease iron and aluminum articles with chemically stable trichlorethylene. Still other objects will be apparent from the ensuing description.

This present invention is based on my discov- In the presence of composition oftrichlorethylene as catalyzed by the presence of aluminum or iron. Diisobutylene is a liquid boiling at about 102 C. which is made by polymerization of isobutylene according to Whitmore, Organic Chemistry, D. Van Nostrand Co. (1937), pages 42-43. It is a mixture of the two isomeric dimers of isobutylene, 2,4,4-trimethylpentene-l boiling at 101.2" C. and 2,4,4- trimethylpentene-Z boiling at 104.5 0., formed in the ratio of 4:1. In the present specification and in the appended claims, the term diisobutylene is used to denote this mixture, whether in a pure state or contaminated with impurities such as other isobutylene polymers. This substance is readily soluble in trichlorethylene and is readily recovered with trichlorethylene when the latter is distilled. Furthermore, this material is unaiiected by any of the decomposition products of trichlorethylene, and it does not increase the solubility of hydrochloric acid in the solvent. I have obtained excellent results by adding 0.1 per cent to 1 per cent by weight of diisobutylene to the trichlorethylene. A definite stabilizing effect can be obtained at still lower concentrations of the stabilizer, e. g., as low as 0.02 per cent by weight. Generally, the solvent is used under conditions where decomposition by oxidation can also occur, and for this reason an antioxidant may also be incorporated in the solvent for optimum results.

I have demonstrated the stabilizing effect of diisobutylene by the following test. Separate portions of trichlorethylene were stored in the absence of air in closed glass containers under identical storage time and conditions. Certain portions, as shown by the following table, contained 0.04 g. per 100 cc. of hydrogen reduced iron powder (about 200 mesh size) and 0.2 g. per

end of the storage period, the samples were analyzed for chloride ion, thereby to determine the degree of decomposition which occurred. The following results were obtained:

None 4 Iron and diisobutylene 22 Aluminum-. 600

Aluminum and diisobutylene 0.8

Diisobutylene .1; 1. 7

the practice of this many and various embodiments thereof may be employed. For instance the trichlorethyle'r'idin addition-filo the diisobutylene, may. also contain one or the known stabilizers against the oxidation position reactions.

. .While trichlorethylene stabilized by the addition of diisobutylenc. iswelhsuited for the various .uses of. this chlorohydrocarbonsolvent, the present invention,is es ecially useful in metal d eas n operations..,W e l1.;. TQIl. or al .num articlesare washed with, trighlqrethyln to "decom- .remove oil. and grease,.. particul arly after machining, operations. ,Th ,yarious known metal :degreasing processesand apparatus may be used for this p rpose in. which hesolv n pe ature may vary from room temperature to the' boiling point. The stabilized trichlorethylene may be applied to the metal articles, for example, by dipping, spraying, or condensation of vapor on the articles.

Iclaimr I I 1. A solvent for degrea'sifi'g iron and aluminum comprising trichlorethylene containing, as stabilizer against condensation reactions of trichlorethylene catalyzed by said metals, 0.02 to 1% by weight of diisobutylene.

2'. A solvent for degreasing iron and aluminum comprisingtriohlorethylene containing, as stabilizer against condensation reactions of trichlor- 'ethylenecatal-yzed by said metals, about 0.1 to 1% by weight of diisobutylene.

' WALTER KLABUNDE.

REFERENCES CITED The following references are of record in the file of this patent:

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